1. Field of the Invention
This invention relates generally to amplifier circuits. More specifically, this invention relates to an amplifier circuit for generating an electrical output responsive to optical signals received over an optical data network.
2. Related Art
Optical data networks provide extremely high throughput over long distances with high resistance to noise. Optical fiber typically routes the optical pulses to their destinations. However, in most instances, those destinations are conventional electrical processing circuits that cannot directly accept or manipulate optical data. As a result, an interface is inserted between the optical network and the electrical processing circuits to convert the optical data into electrical pulses.
Some interfaces employ a photodiode to detect the optical signal and output a low-level electrical detection signal. A subsequent amplification stage coupled directly to the photodiode boosts the low level electrical signal to create a useful output signal representative of the optical signal originally received. In the past, however, this approach has suffered from several drawbacks.
In particular, the photodiode is often only responsive enough to create a very small response signal. For that reason, the subsequent amplification stage must employ tremendous levels of amplification to generate an output signal at a level appropriate for subsequent processing electronics. All circuits, however, are characterized by a certain amount of noise. For this reason, the small detection signal often drowns in the input noise of the amplification stage. While the output signal includes a contribution from the response signal, the output signal is overwhelmingly noise. The response signal is thus lost, along with the data it represented. Therefore, there is a need for overcoming the problems noted above, and other previously experienced.